Birefringence of mechanically clamped TGS crystals with L-valine admixture

The influence of uniaxial mechanical stresses applied along the crystal-physical axes on the principal values of the birefringence, n i , was studied for TGS crystals with 5% L-valine admixture. It was found that n i are quite sensitive to stress and adopt different values and opposite signs, when compared to pure TGS. The baric coefficients c / m for the phase transition (PT) temperature appear to be less than for pure TGS. The temperature dependence of the combined piezooptic constants 0 im was calculated. The values of the jumplike changes occurring for all the piezooptic constants at the PT are notably lower for the doped crystals than for pure TGS. Birefringence / Uniaxial pressure / Phase transitions / Piezooptic constants